Shell Bitumen - Cariphalte - Megget Resevoir Case Study

SHELL CARIPHALTE
Bitumenous grouting to repair and protect the reservoir
supplying Scotland’s capital city with water
CASE STUDY: MEGGET RESERVOIR
The Megget reservoir, in the Borders region
of Scotland, holds 64,000 mega litres of
water to supply the city of Edinburgh and its
450,000 residents. It supplies 100 million
litres of water daily. In the first project of its
kind in the world, bitumenous grouting was
used to repair and reinforce protection for a
reservoir embankment.
The 56m high by 570m long dam is a gravel
filled embankment with a central asphaltic core.
The reservoir is retained by the largest earth dam in
Scotland. The upstream face of the dam is protected
against wave action erosion by graded quarry rock,
known as ‘rip-rap’, on a granular filter.
First project of its kind in the world - bitumenous grouting
used to repair Scotland biggest earth dam reservoir
Critical Success Factors: Allowed reservoir to continue operating
Maintained fish stock
Minimal maintenance required
Low installation costs
Application: Bitumens grout
Volume: 1,100 tonnes of 100 pen bitumen supplied
Product family: Shell Cariphalte
Client: East od Scotland Water
Contractor: Hesselberg Hydro
Project Engineer: Whatlings (Civil Engineering) Ltd

This has suffered continuous erosion since 1983 when the
reservoir was filled and a wind-wave investigation showed that
waves were greater than designers had anticipated. Repairs
had to be carried out on an ongoing basis, resulting in high
maintenance costs and considerable disruption.
Bitumenous grouting offers the best long term solution
East Scotland Water undertook a study to evaluate methods for
upgrading the existing rip-rap protection layer to ensure minimal
maintenance and long term service. Options assessed included
the installation of an additional layer using bigger rock elements,
a shallower upstream slope angle, concrete block work or
bituminous grouting.
The contractors, Hesselberg Hydro, undertook on-site trials and
visited asphaltic coastal defence structures in Holland which
suffered a similar wave attack. As a result of extensive research,
they selected bituminous grouting.
“The Megget reservoir supplies 100 million
litres of water daily and is the first project
of its kind in the world. Bitumenous grouting
was used to repair and reinforce protection
for a reservoir embankment.”
Bituminous grout is an homogeneous mixture of mastic, consisting
of penetration grade bitumen, limestone filler and natural medium
to fine sand, together with small graded crushed stone or gravel.
For further information
please contact your Shell Bitumen
representative or visit;
www.shell.com/bitumen
The Shell emblem, Cariphalte and SHELL are trade marks of the Shell Group.
03/2011/ CS5
A tailored solution
The Shell Bitumen team came on board and were able to quickly
add value to the project, working in close collaboration with the
main contractors, Hessel Hydro, advising on the best application
method and product mix.
A pattern grouting technique was selected to provide maximum
strength, while also limiting the amount of grout, and maintaining
adequate porosity of the rock layer to dissipate the hydraulic
energy of breaking waves and water pressure. It also provided
the most economical long-term solution.
The viscosity of the mixture was critical to ensure the grouting
penetrated the full depth of the rip-rap layer, but also gave sufficient
stability to the existing rock after cooling, without sagging at
ambient temperatures on the steep slope of the embankment.
The most economic and practical solution
Full scale site trials prior to the award of the main contract
demonstrated the increased strength of the rock layer while
retaining adequate porosity
27,000m 2 upgraded with pattern grouting on a 2.5m grid
On site production of 10,500 tonnes of mastic
Full using made of mobile quality control laboratory
Mastic grout applied hot from specially designed skips,
penetration relying on gravity
Completion was on time in and within budget.